Objective: To examine if dual replacement with insulin and rhIGF-I, recombinant human insulin-like growth factor I (rhIGF-I) may be safe and result in improved metabolic control and reduced insulin usage.
Research design and methods: Forty-three patients with IDDM were randomized to receive a daily injection of rhIGF-I (80 mcg/kg s.c.) or placebo while on conventional insulin therapy for 4 weeks. Insulin was adjusted in the attempt to achieve predetermined goal glycemic values. Free and total IGF-I, four daily blood glucoses, and HbA1c were measured.
Results: Before randomization, placebo and rhIGF-I groups exhibited low plasma levels of free and total IGF-I, which increased toward normal levels during the treatment period only in the rhIGF group. The regression curve obtained from the average of daily blood glucose measurements indicated that the glycemic profile, overlapping in the lead-in period, exhibited a downward trend in the rhIGF-I group during the treatment period. Mean blood glucose level during the last 10 days of treatment was lower in the rhIGF-I groups (174 +/- 37 vs. 194 +/- 32 mg/dl). HbA1c level was reduced by more than one-half percent more in the rhIGF-I group (-1.85%) than in the control group (-1.3%). The dose of regular insulin was significantly lower in the rhIGF-I group (0.2 +/- 0.1 vs. 0.28 +/- 0.1 U. kg-1. 10 days-1 in the placebo group; P < 0.05).
Conclusions: rhIGF-I in combination with conventional insulin treatment ameliorated the low plasma total and free IGF-I levels and was well tolerated in IDDM. There was a trend toward improved glycemic control, while the regular insulin dose was significantly decreased.